What are the “antibodies?
There are two different kinds of antibodies. There are what we call “expected antibodies” — this means for example that someone who is blood type “A” will have in their serum “anti B”. The person who is type “B” will have in their serum “anti A”. A person who is type “O” will have in their serum “anti A” and “anti B” and the person who is blood type “AB” will have neither “anti A” nor “anti B” in their serum. As a matter of fact when we do a blood type, we not only look into red cell to see whether they are type “A” type “B” type “AB” or type “O”, but we also look at the serum for antibodies that we expect to be there. There are other red cell antigens though, that people can make antibodies to if they get exposed to those red cells. These antibodies are what we call “unexpected antibodies”. We don’t expect them to normally be present, but when people get transfused, when they have organ transplants or when women are pregnant, they get exposed to foreign tissues and they can make anti
